408 BULLETIN OF THE BUREAU OF FISHERIES. 



This division, well represented in most regions, here forms a very small part of the 

 marine flora, only 10 genera and 10 species having been obtained in quantities sufficient 

 for determination. 



KEY TO ORDERS. 



Plants unicellular, single, or associated in families, which are usually surrounded by a gela- 

 tinous integument, not filamentous i. COCCOGONE/E (p. 408). 



Plants multicellular (except Spirulina), filamentous 2 . HORMOGONE^ (p. 409). 



OrUer 1. Coccogonese (Thuret) Kirchner. 



Plants unicellular, single, or associated in families or colonies, which are' usually 

 surrounded by a copious gelatinous integument, rarely forming filaments; multiplica- 

 tion occurs commonly by the vegetative division of cells, rarely by the formation of foHr 

 or more nonmotile gonidia arising from the division of the contents of a cell 

 (gonidangium). 



Family 1. CHROOCOCCACE^E Naegeli. 



Cells solitary or associated in families, showing no difference between basal and 

 apical regions; multiplication usually by simple division of the cells. 



Unicellular algae, entirely uniform, occurring singly or more often in clusters which 

 are conspicuous even to the naked eye, the cells grouped without order in a common 

 sheath. Cells spherical, oval or elongate, sometimes fusiform, cuneate, or squarish. 

 Extremely minate bodies containing diffuse blue, aeruginous, or even purple, olive, 

 brown, or yellow coloring matter occur in the cells. The cell wall is sometimes 

 thin and delicate, sometimes thick, often surrounded by a structureless, gelatinous 

 sheath which holds the cells together for many generations and forms families variable 

 in number and appearance of the cells. Divisions usually in three planes forming 

 families irregularly grouped, but also in two planes forming layers of sheetlike families, 

 or even in one plane, forming families at first linear, then by mechanical action irregularly 

 grouped and contorted. Propagation in the Chroococcaceae living singly does not occur 

 except by the vegetative division of the cells, in those species living gregariously it occurs 

 either by the separation of a single cell or by the splitting up of an old family into several 

 families. Spores provided with a thickened resistant wall have been observed occa- 

 sionally in species of Gloeocapsa; these arise from the vegetative cells and are formed 

 by the repeated division of the contents or by the dissolution of the membrane. 



About 300 species, mostly in fresh water, less often in salt water or in damp places 

 or aerial, throughout the world. 



Genus Chroococcus Naegeli. 

 Chroococcus Naegeli, 1849. P- 45- 



Cells globose, or by mutual pressure more or less angular, each surrounded by a 

 more or less definite sheath ; solitary or associated in families composed of two or four, 

 rarely more, individuals, but not held together in definite colonies by a common gelat- 

 inous sheath; cell wall thin or wide, homogeneous or lamellose, colorless or colored; 

 cell contents homogeneous or granular, aeruginous or blue-green, sometimes yellowish or 

 orange or violet; multiplication by successive division of the cells alternately in three 

 planes; free floating or forming a gelatinous or crustlike mass in damp places. 



